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Plasma membrane overgrowth causes fibrotic collagen accumulation and immune activation in Drosophila adipocytes.

Zang Y, Wan M, Liu M, Ke H, Ma S, Liu LP, Ni JQ, Pastor-Pareja JC - Elife (2015)

Bottom Line: Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion.Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response.It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
Many chronic diseases are associated with fibrotic deposition of Collagen and other matrix proteins. Little is known about the factors that determine preferential onset of fibrosis in particular tissues. Here we show that plasma membrane (PM) overgrowth causes pericellular Collagen accumulation in Drosophila adipocytes. We found that loss of Dynamin and other endocytic components causes pericellular trapping of outgoing Collagen IV due to dramatic cortex expansion when endocytic removal of PM is prevented. Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion. Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response. Our work indicates that traffic imbalances and PM topology may contribute to fibrosis. It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

No MeSH data available.


Related in: MedlinePlus

Immune response to fibrotic deposits.(A) Melanotic fat body in a ppl>shii fly. (B) Melanized fat body from an r4>shii larva. Hemocytes (blood cells) encapsulate the tissue. (C) Knock-down of Collagen IV reduces fat body melanization in r4>shii larvae. Cultures maintained at 30°C. (D) Percentage of larvae displaying signs of melanization in indicated genotypes. n ≥ 30 per genotype. Differences with r4>shii and >Tl10B controls were significative (χ2 tests, ***p < 0.001). Cultures maintained at 30°C. (E) Induction of c-Jun N-terminal kinase (JNK) downstream puckered (puc-GFP enhancer trap) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (F) Induction of Matrix Metallo-Protease 1 (anti-Mmp1 staining) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (G) Expression of JAK/STAT activity reporter 10XSTAT-GFP in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (H) Expression of JAK/STAT-activating ligands in wild type, BM-40-SPARC>shii and >Tl10B adipocytes assessed by real time RT-PCR. Error bars represent 95% confidence intervals. rp49 expression was used for normalization.DOI:http://dx.doi.org/10.7554/eLife.07187.016
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fig7: Immune response to fibrotic deposits.(A) Melanotic fat body in a ppl>shii fly. (B) Melanized fat body from an r4>shii larva. Hemocytes (blood cells) encapsulate the tissue. (C) Knock-down of Collagen IV reduces fat body melanization in r4>shii larvae. Cultures maintained at 30°C. (D) Percentage of larvae displaying signs of melanization in indicated genotypes. n ≥ 30 per genotype. Differences with r4>shii and >Tl10B controls were significative (χ2 tests, ***p < 0.001). Cultures maintained at 30°C. (E) Induction of c-Jun N-terminal kinase (JNK) downstream puckered (puc-GFP enhancer trap) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (F) Induction of Matrix Metallo-Protease 1 (anti-Mmp1 staining) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (G) Expression of JAK/STAT activity reporter 10XSTAT-GFP in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (H) Expression of JAK/STAT-activating ligands in wild type, BM-40-SPARC>shii and >Tl10B adipocytes assessed by real time RT-PCR. Error bars represent 95% confidence intervals. rp49 expression was used for normalization.DOI:http://dx.doi.org/10.7554/eLife.07187.016

Mentions: Our experiments indicated that fibrotic aggregates could form downstream of Toll immune signaling. We therefore decided to characterize further the immune effects of these deposits. In our screening, 32 out of 70 hits producing pericellular Collagen IV accumulation showed clear signs of a fat body melanization response, including cact, shi, Rab5 and Chc (Supplementary file 1). Melanization is an insect immune response characterized by blackening of the affected tissue, usually accompanied by hemocyte (blood cell) recruitment (Minakhina and Steward, 2006). Because BM-40-SPARC-GAL4 and Cg-GAL4, the strong fat body drivers we had used so far, are also expressed in blood cells, we tested weaker fat body drivers ppl-GAL4 and r4-GAL4, inactive in blood cells, and found that melanization still occurred (Figure 7A,B), ruling out that interfering with blood cell function caused the response. Furthermore, confirming the involvement of Collagen deposits in the response, both the number of r4>shii larvae displaying melanization and the extent of it decreased when we additionally knocked down Collagen IV or PH4αEFB (Figure 7C,D). Reduction of Collagen IV and PH4αEFB also reduced melanization of r4>Toll10B larvae (Figure 7D) and completely rescued their pupal lethality. These results show that Collagen deposits either trigger or significantly contribute to fat body melanization in these conditions.10.7554/eLife.07187.016Figure 7.Immune response to fibrotic deposits.


Plasma membrane overgrowth causes fibrotic collagen accumulation and immune activation in Drosophila adipocytes.

Zang Y, Wan M, Liu M, Ke H, Ma S, Liu LP, Ni JQ, Pastor-Pareja JC - Elife (2015)

Immune response to fibrotic deposits.(A) Melanotic fat body in a ppl>shii fly. (B) Melanized fat body from an r4>shii larva. Hemocytes (blood cells) encapsulate the tissue. (C) Knock-down of Collagen IV reduces fat body melanization in r4>shii larvae. Cultures maintained at 30°C. (D) Percentage of larvae displaying signs of melanization in indicated genotypes. n ≥ 30 per genotype. Differences with r4>shii and >Tl10B controls were significative (χ2 tests, ***p < 0.001). Cultures maintained at 30°C. (E) Induction of c-Jun N-terminal kinase (JNK) downstream puckered (puc-GFP enhancer trap) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (F) Induction of Matrix Metallo-Protease 1 (anti-Mmp1 staining) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (G) Expression of JAK/STAT activity reporter 10XSTAT-GFP in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (H) Expression of JAK/STAT-activating ligands in wild type, BM-40-SPARC>shii and >Tl10B adipocytes assessed by real time RT-PCR. Error bars represent 95% confidence intervals. rp49 expression was used for normalization.DOI:http://dx.doi.org/10.7554/eLife.07187.016
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Related In: Results  -  Collection

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fig7: Immune response to fibrotic deposits.(A) Melanotic fat body in a ppl>shii fly. (B) Melanized fat body from an r4>shii larva. Hemocytes (blood cells) encapsulate the tissue. (C) Knock-down of Collagen IV reduces fat body melanization in r4>shii larvae. Cultures maintained at 30°C. (D) Percentage of larvae displaying signs of melanization in indicated genotypes. n ≥ 30 per genotype. Differences with r4>shii and >Tl10B controls were significative (χ2 tests, ***p < 0.001). Cultures maintained at 30°C. (E) Induction of c-Jun N-terminal kinase (JNK) downstream puckered (puc-GFP enhancer trap) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (F) Induction of Matrix Metallo-Protease 1 (anti-Mmp1 staining) in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (G) Expression of JAK/STAT activity reporter 10XSTAT-GFP in BM-40-SPARC>shii, >Tl10B and >cacti adipocytes. (H) Expression of JAK/STAT-activating ligands in wild type, BM-40-SPARC>shii and >Tl10B adipocytes assessed by real time RT-PCR. Error bars represent 95% confidence intervals. rp49 expression was used for normalization.DOI:http://dx.doi.org/10.7554/eLife.07187.016
Mentions: Our experiments indicated that fibrotic aggregates could form downstream of Toll immune signaling. We therefore decided to characterize further the immune effects of these deposits. In our screening, 32 out of 70 hits producing pericellular Collagen IV accumulation showed clear signs of a fat body melanization response, including cact, shi, Rab5 and Chc (Supplementary file 1). Melanization is an insect immune response characterized by blackening of the affected tissue, usually accompanied by hemocyte (blood cell) recruitment (Minakhina and Steward, 2006). Because BM-40-SPARC-GAL4 and Cg-GAL4, the strong fat body drivers we had used so far, are also expressed in blood cells, we tested weaker fat body drivers ppl-GAL4 and r4-GAL4, inactive in blood cells, and found that melanization still occurred (Figure 7A,B), ruling out that interfering with blood cell function caused the response. Furthermore, confirming the involvement of Collagen deposits in the response, both the number of r4>shii larvae displaying melanization and the extent of it decreased when we additionally knocked down Collagen IV or PH4αEFB (Figure 7C,D). Reduction of Collagen IV and PH4αEFB also reduced melanization of r4>Toll10B larvae (Figure 7D) and completely rescued their pupal lethality. These results show that Collagen deposits either trigger or significantly contribute to fat body melanization in these conditions.10.7554/eLife.07187.016Figure 7.Immune response to fibrotic deposits.

Bottom Line: Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion.Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response.It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
Many chronic diseases are associated with fibrotic deposition of Collagen and other matrix proteins. Little is known about the factors that determine preferential onset of fibrosis in particular tissues. Here we show that plasma membrane (PM) overgrowth causes pericellular Collagen accumulation in Drosophila adipocytes. We found that loss of Dynamin and other endocytic components causes pericellular trapping of outgoing Collagen IV due to dramatic cortex expansion when endocytic removal of PM is prevented. Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion. Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response. Our work indicates that traffic imbalances and PM topology may contribute to fibrosis. It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

No MeSH data available.


Related in: MedlinePlus